Scrubbers are used in chemical processes to separate or eliminate compounds and come in several different variations. The wet scrubber can separate impurities out of a gaseous stream by passing a wet scrubbing reagent through the gas to absorb the impurities. Examples of wet scrubbing reagents include lime slurries, sodium hydroxide solutions, bromine, nitric acid, ammonia, and water. The wet scrubber is one of the most common pollution control devices used by industry. It operates on a very simple principle: a polluted gas stream is brought into contact with a liquid so that the pollutants can be absorbed. The dry scrubber operates in a similar manner as the wet scrubber, except that a dry scrubbing reagent is sprayed on the gaseous stream being treated. Examples of dry scrubbing reagents include lime powder and carbon powder. Semi-dry scrubbers are another type of scrubber, and these generally use slurries that are atomized into fine droplets and then sprayed into the gaseous stream. The fine droplets quickly dry out in the high temperature of the scrubber prior to interacting with the gaseous stream. Finally, there are scrubbers that operate as incinerators or flare stacks, where a gaseous stream is mixed with combustible gases and then ignited. Typical combustible materials used here include oxygen and natural gas.
In many chemical processes, gaseous streams to be cleaned or burned are delivered to a scrubber in a non-continuous manner. Despite this fact, scrubbers in most chemical processes are continuously operated even when there are no gaseous streams to be treated. This results in an excess consumption and waste of scrubbing reagents or combustible materials, such as oxygen and natural gas, when the scrubber is simply running while waiting for a gaseous stream to arrive. Furthermore, since water (e.g., recycled city water) is often used by most scrubbers to remove by-products of the scrubbing process, water is also wasted when there is no gaseous stream to treat. Accordingly, better methods of scrubbing gaseous streams are desired.